Danique Kerkdijk gave Albion the lead before Alisha Lehmann struck twice to give the Hammers a victory, and Powell bemoaned a lack of cutting edge in front of goal.
She said, “We should’ve won the game, but if you don’t take your chances then you give the opposition more of an opportunity to stay in the game.
“Credit goes to West Ham because they came out on the front foot in the second half and we didn’t react very well.
“We took a bit of time to settle, but we’ve got to score with the chances we created, and that’s very disappointing.
“I thought we played well again. We played well against Arsenal, against Man United and again today, but if you don’t score it means nothing. I’m pleased in that respect, but not so pleased that we can’t finish.”
Powell reflected on what has been a gruelling period for her side after three games in the space of seven days, as attention now turns to an FA Cup fourth round tie away at Aston Villa next week.
“We’ve played three games in seven days, and that is tough. The players are tired, so we need to give them some time off and then we’ve got to go again.
“It’s a very harsh lesson, as there were three points to win and I think we lost the points ourselves. You have to reflect, come back, let it go and move on.
“Now we look ahead to an FA Cup game against Aston Villa, who we know are a decent side that’s top of the league. It will be a challenging game for us, but we’ll prepare for it like any other.”